On my wallet, it shows I only transfer 0.05 btc to the exchange "BTCC". But on bitcoin block explorer, it is showed that I transferred 0.05+4 btc.
your wallet only shows the amount leaving your wallet, which as you said 0.05 btc
while block explorer shows the full details on that transaction
you can see the same on your bitcoin core by opening the transaction details on your transaction
for technicalities, LoyceV and bob123 has explained pretty clear on their posts
My bitcoin number shown on my bitcoin core wallet is different with the record on bitcoin block explorer.
bitcoin core wallet shows total bitcoin you have in your wallet, in multi addresses that you have
block explorer shows balance only on specific bitcoin address, they don't know all addresses in your wallet